JPH03250678A - Laser device - Google Patents

Abstract

PURPOSE:To buffer mismatching in circuit conditions with respect to a change in a discharge input so as to suppress reflected wave power to a high frequency power source by using a self-exciting power source whose oscillation frequency changes along with a fluctuation in load of high frequency discharge as the high frequency power source. CONSTITUTION:High frequency power generated in a high frequency oscillating part 20 is supplied via transformer coupling 22 to a higher voltage electrode 6a and a lower voltage electrode 6b of a laser discharge part. Discharge resistance on the load side viewed from the transformer coupling 22 depends on a ratio in numbers of windings between the primary side and the second side of the transformer and can be expressed in a resistance value on the primary side. Therefore change in discharge resistance changes oscillation frequency of the high frequency oscillating part 20. Discharge resistance increases along with an increase in a discharge input of the high frequency discharge and discharge resistance decreases along with an increase in oscillation frequency. When the discharge resistance drops, an equivalent resistance value drops so that oscillation frequency increases, thereby permitting a high frequency power source itself to be kept in a matching state. Therefore even if the discharge input is varied, mismatching between a discharge part and the high frequency power source can be relaxed.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention applies a high-frequency voltage between high-voltage side and low-voltage side electrodes using a high-frequency power source, and generates a high-frequency discharge across a dielectric. This invention relates to a laser device that performs.

(Conventional technology) Laser gas pressure number 10 tons used for various laser processing
FIG. 4 shows an example of a laser device that performs laser excitation by generating high-frequency discharge at about 200 torr.

Note that FIG. 4 shows a high frequency power source and a laser oscillation section. That is, the high frequency power supply 1 has an excitation section 2 and a power amplifier section 3.
The high frequency power of the frequency f (usually 13°56 HM z±2KHz) generated in the excitation part 2 is
It is amplified by the power amplifier section 3 and then passed through the matching box 5 for impedance matching by the coaxial cable 4 having a characteristic impedance of 50Ω, and then the high voltage side electrode 6 of the laser discharge section.
supplied to a. On the other hand, the low voltage side electrode 6b is grounded.

Further, the high frequency voltage supplied between the high voltage side electrode 6a and the low voltage side electrode 6b is applied to the laser gas via dielectrics 7a and 7b arranged adjacent to each electrode, generating a high frequency discharge 8. let Although not shown in the figure, in order to prevent the gas temperature from rising due to high frequency discharge, dielectrics 7a, 7
Laser gas is flowing between b. Furthermore, by arranging a reflecting mirror 9 and a partial reflecting mirror 10 with the high-frequency discharge 8 in between to form a laser resonator, laser oscillation is performed and laser light 11 is obtained. Note that when it is necessary to modulate the laser beam 11, the pulse modulation signal 12 may be sent to the excitation section 2 from the outside.

On the other hand, the power amplifier section 3 includes a vacuum tube 13 for amplifying high frequency signals, and a capacitor C for adjusting output impedance.
, C2 and an inductance L1, a high DC voltage is applied to the vacuum tube 13 to operate the vacuum tube, and a capacitor C3 is connected to prevent this DC from passing through to the high frequency output side. has been done. Further, the matching device 5 for impedance matching is of an inverted type and is composed of a variable capacitor C4 and an inductance L2.

(Problems to be Solved by the Invention) However, in the conventional laser device having the above configuration, there were problems to be solved as described below.

That is, as the discharge input changes, the discharge resistance changes, causing a mismatch with the output impedance of the high-frequency power source 1, and accordingly, reflected wave power is generated, which adversely affects the high-frequency power source 1. Further, although the conventional laser device has very good pulse control performance, the high frequency power source 1 itself is very expensive.

The present invention was proposed in order to eliminate the drawbacks of the prior art as described above, and its purpose is to alleviate the mismatch of circuit conditions in response to changes in discharge input, and to reduce the reflected wave power from the high frequency power source. An object of the present invention is to provide an inexpensive laser device that can suppress the noise.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a laser device that applies a high frequency voltage between a high voltage side electrode and a low voltage side electrode using a high frequency power supply to generate a high frequency discharge across a dielectric. The above-mentioned high-frequency power source is characterized in that a self-excited power source whose oscillation frequency changes in accordance with load fluctuations of high-frequency discharge is used.

(Function) Since the laser device of the present invention uses a self-excited power source as a high-frequency power source, it is possible to vary the oscillation frequency by about 10% of the oscillation frequency f determined by the glue C1 in the oscillation circuit. I can do it.

Therefore, the frequency of the high-frequency power source can be varied in response to the change in discharge impedance depending on the discharge input, so that the mismatch state with the discharge section can be alleviated.

(Example) Hereinafter, an example of the present invention will be specifically described based on FIG. Incidentally, the same members as those of the conventional type shown in FIG. 4 are given the same reference numerals, and explanations thereof will be omitted.

As shown in FIG. 1, the laser device of this embodiment is composed of a self-excited high-frequency power source and a laser oscillation section (discharge section). That is, the high-frequency oscillation section 20 of the high-frequency power supply is composed of a Colpitts circuit that easily extracts high frequencies to the discharge load side by transformer coupling, and a vacuum tube (for oscillating high frequencies).
triode) 21, capacitor C5 that determines the oscillation frequency f,
It is composed of C6 and an inductance 3 which also serves as a coupling transformer with the load. Further, a high DC voltage is applied to the vacuum tube 21 to operate the vacuum tube.
Furthermore, a capacitor C7 is installed to prevent this direct current from passing through to the high frequency output side.

Further, the high frequency power of the frequency f (±10% in terms of frequency fluctuation range) generated in the high frequency oscillator 20 is transmitted to the transformer coupling 2
2 to the high voltage side electrode 6a and low voltage side electrode 6b of the laser discharge section. here,
The transformer coupling 22 connects the negative side and the secondary side so that the output impedance of the high frequency oscillation section 20 and the impedance of the laser discharge section can be matched under a certain discharge input condition (for example, maximum discharge input). The turns ratio is adjusted.

In addition, at this time, the oscillation frequency f generated in the high frequency oscillator 20 is f=1/2π, v' 1 /L3 ・(1/C+ +
1 /C2)...(1), and the oscillation frequency f changes with fluctuations in the discharge load, which acts to soften the reflected power due to the mismatch state. Further, in the case of this embodiment, when pulse modulating the laser beam 11, it is sufficient to send the pulse modulation signal 12 to the grid of the vacuum tube 21 from the outside.

The operation of the laser device of this embodiment having such a configuration will be described below.

That is, in the laser device of this embodiment, the discharge resistance r viewed from the transformer coupling 22 to the load side is expressed as the negative side resistance value in a relationship that depends on the turn ratio of the primary and secondary sides of the transformer. be able to. Therefore, when considering the circuit of FIG. 1 equivalently, the discharge resistance r on the secondary side can be regarded as a resistance R connected in series with the inductance L3 on the primary side.

That is, in the case of an ideal transformer, if the number of turns on the negative side and the secondary side are n 1 + n 2, then R = (n
+ /n2) 2gei r. Also, at this time, the oscillation frequency f of the high frequency oscillation section 20. By considering a parallel resonant circuit, fo=1/
2π ・J 1 /L3 ・(L/CI +1 /C2)−R
2/L 2...(2) It is expressed as. Therefore, the oscillation frequency f of the high frequency oscillator 20 changes due to a change in the discharge resistance r. can be seen to change.

Further, the effects of this embodiment will be explained with reference to FIGS. 2 and 3. That is, in FIG. 2 showing the relationship between the discharge input and the discharge resistance r, the discharge resistance r increases as the discharge input of high-frequency discharge increases, and the oscillation frequency f. In FIG. 3, which shows the relationship between the oscillation frequency f and the discharge resistance r. It can be seen that the discharge resistance r decreases with an increase in . In this embodiment, the discharge input is set to 100 OW so that the discharge circuit can be matched at an oscillation frequency of 10 MHz. For example, if the discharge input is lowered at this time, the discharge resistance r will decrease as shown in Figure 2, but in conventional laser devices, the oscillation frequency does not change, so the matching state of the discharge circuit is Unsatisfied, the reflected power returned to the high-frequency power source, adversely affecting the high-frequency power source. However, in this embodiment, the oscillation frequency f is determined according to equation (2). changes. That is, when the discharge resistance r decreases, the equivalent resistance value R decreases, so the oscillation frequency fo increases, and as a result, the high frequency power source itself acts to maintain a matching state. Therefore, even if the discharge input is changed, the mismatch between the discharge section and the high frequency power source can be alleviated.

In this way, according to this embodiment, the mismatch between the high frequency discharge section and the high frequency power source can be alleviated, and the adverse effect on the high frequency power source due to the reflected power caused by the mismatch can be eliminated. Furthermore, since the configuration is simple, a high frequency power source for a laser can be obtained which is cheaper than a conventional high frequency power source.

Note that the present invention is not limited to the embodiments described above, and similar effects can be obtained even if the self-excited high-frequency power source is constructed using a semiconductor. Furthermore, a matching box may be used in the load circuit on the secondary side.

[Effects of the Invention] As described above, according to the present invention, as a high frequency power source,
By using a self-excited power supply whose oscillation frequency changes with fluctuations in the high-frequency discharge load, it is possible to alleviate mismatches in circuit conditions and suppress reflected wave power from the high-frequency power supply in response to changes in discharge input. , an inexpensive laser device can be provided.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the laser device of the present invention;
FIG. 2 is a diagram showing the relationship between discharge input and discharge resistance, FIG. 3 is a diagram showing the relationship between oscillation frequency and discharge resistance, and FIG. 4 is a circuit diagram showing an example of a conventional laser device. DESCRIPTION OF SYMBOLS 1... High frequency power supply, 2... Excitation part, 3... Power amplifier part, 4... Coaxial cable, 5... Matching box, 6
a...High voltage side electrode, 6b...Low voltage side electrode, 7a
, 7b... dielectric, 8... high frequency discharge, 9... reflecting mirror, 10... partial reflecting mirror, 11... laser light, 1
2...Pulse modulation signal, 13...Vacuum tube, 20...
・High frequency oscillation section, 21...vacuum tube, 22...transformer coupling.

Claims (1)

[Scope of Claims] A laser device that applies a high-frequency voltage between a high-voltage side electrode and a low-voltage side electrode by a high-frequency power source to generate a high-frequency discharge across a dielectric, wherein the high-frequency power source has an oscillation frequency that is high-frequency. A laser device characterized by using a self-excited power source that changes with discharge load fluctuations.